Social Desirability (SD) bias refers to the tendency of research subjects to give socially desirable responses instead of choosing responses that are reflective of their true feelings. The bias in responses due to this personality trait becomes a major issue when the scope of the study involves socially sensitive issues such as politics, personal issues such as drug use, cheating, smoking. and medication-taking. Whenever possible, it is desirable to measure the extent of the bias present in responses to a survey by incorporating a socially desirable scale in the survey. This is particularly a bias when we use indirect methods, such self-reported questionnaires.
The MMAS-8 was conceptualized to reduce the presence of SD by reversing the direction of the question. The MMAS-8 never asks the parient "Do you always take your high blood pressure medication" because 90% of my patients will say "yes, doctor". So, we ask in the negative direction, "Do you sometimes forget to take your high blood pressure medication"? Now about 50% will respond "yes".
Dr Donald Morisky.